Chronic cervical vibration ameliorates depression-like behavior in Wistar-Kyoto rats
Major depressive disorder (MDD) is a highly prevalent psychiatric condition, and a substantial proportion of patients exhibit inadequate responses to conventional pharmacotherapy. Somatosensory processing abnormalities and altered thalamo-cortical connectivity have been implicated in the pathophysiology of MDD, raising the possibility that targeted somatosensory stimulation may modulate affective circuits. Here, we examined whether chronic cervical vibration improves depression-like behaviors in Wistar-Kyoto (WKY) rats, a well-established model of treatment-resistant depression. Rats received repeated vibration stimulation applied to the cervical region. Behavioral effects were evaluated using the novelty-suppressed feeding test (NSFT) and the forced swim test (FST). Swimming activity was quantified during the late-phase of the FST to exclude early panic-like behavior. Immunohistochemistry for c-Fos was performed in the dorsal raphe (DR), lateral habenula (LHb), paraventricular nucleus of the hypothalamus (PVN), and prefrontal cortex (PFC). Vibration-treated rats showed significantly shorter feeding latencies in the NSFT and significantly increased swimming distance during the analysis period of the FST. No significant group differences in c-Fos expression were observed in DR, LHb, PVN, or PFC. These findings indicate that chronic cervical vibration produces reproducible improvements in depressive-like behavior in WKY rats. Because c-Fos activity remained unchanged, the behavioral effects may reflect gradual changes in broader network processing rather than acute activation of monoaminergic or habenular-prefrontal pathways. Cervical vibration represents a simple, non-invasive sensory intervention with translational potential. Additional mechanistic studies are warranted.